An Implementation of Explicit Delay-Control Algorithm

Motivation: The worldwide fever for interactive multimedia applications is soaring due to great proliferation of the Internet and abundance of broadband. Most of these applications (e.g. video telephony, networked multiplayer game) are highly delay-sensitive, therefore depend on the support from the networks. A key requirement is packets that are out of delay boundary are obsolete for the application. However the best-effort nature of the Internet poses many challenges for latency and jitter solicited by real-time flows. The Time of Live (TTL) Field of IPv4 was designed with two functions in mind: to limit the lifetime of an IP packet, and to terminate Internet routing loops. It is a value expressed in seconds and each router along the path is supposed to decrement the TTL by one. In reality, TTL is rather a hop count for the maximum number of hops a packet can traverse in the network, than an indication of the packet lifetime. This is the reason why it has been renamed as HopLimit in IPv6 to reflect its real usage. TTL dose not really indicate precisely the lifetime of a packet. Moreover, the time unit used by TTL is second, this is by far not the resolution needed for time-critical interactive multimedia applications that normally require a one-way delay within 100ms. Hereby, a new approach from IP itself (apart from existing QoS mechanisms) has to be in place to take the responsibility of explicit packet lifetime control with high degree of accuracy, for delay-sensitive real-time traffic over the Internet.

Tasks: In this project, the student will implement our algorithm of Explicit Delay Control on a test-bed that consists of a number of end-systems and IP routers. The student will start with the study of end-to-end delay analysis on time-critical interactive multimedia applications, the existing QoS approaches, and the details of the EDC Algorithm. This will be followed by the study of the code of TCP/IP Stack within Linux kernel, and experiments on Linux kernel programming. The core of the project will then be the implementation of the EDC Algorithm into the kernel and validate and evaluate the algorithm under realistic traffic patterns. The result of the work is supposed to be written down as a technical report and an internal presentation is required at the end of the project.

Prerequisite: Basic knowledge of computer networks, and skills in C/C++ programming in Linux.

Supervisors: Xiaoyuan Gu(IBR)

Duration: June 2004 – September 2004

• Project Report: Implementation of Explicit Delay Control Algorithm